To perform the experiments, we let one C57BL/6J wildtype animal freely explore a circular arena with a transparent Plexiglas floor.
We recorded 60 minutes of unconstrained behavior using 5 synchronous cameras operating at 50 Hz that have been mounted as shown in Figure REF .
We then labeled 8 body parts in \(1e3\)  images and trained a ResNet CNN model provided in the DeepLabCut 2.2 [1]} to detect the keypoints from the bottom view as well as side view recordings (Figure REF ).
The image augmentation routines supplied in the DeepLabCut package were used to improve the generalization of the network.
The keypoint coordinates were egocentrically aligned, so that the nosetip and tailbase marker form a vector parallel to the \(x\) -axis and the center of the animal body is approximately at the origin of the \(x\)  and \(y\)  axes.
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